Temperature control device



TEMPERATURE CONTROL DEVICE Filed Sept. 26, 1939 F gg1 Z9 5 j 3 I; 2/ J14 534; g I H 14 a 24171; m /z Z9 /6 /5 7f Pi .3. 04 a! if M I M J/JZ Z I i If: 45 an a a a :7 6! I 4s 1 j I a y," w 4 M I a a w' a W I I I a a v i 2.9 22 z/ E 7,; :6 I 4 :7 l6 Fi 6+ Inventor:

Q Wal InceIEttinQer;

HisA tovne y,

Patented Mar. 3, 1942 TEMPERATURE CONTROL DEVICE Wallace J. Ettinger, Chicago, Ill., assignor to Edison General Electric Appliance Company, Inc., Chicago, 111., a corporation of New York Application September 26,1939, Serial No. 296,611

14 Claims.

This invention relates to a control device for controlling an electric circuit in accordance with temperature changes and more specifically relates to a control device which is adapted to be actuated with a snap action. More specifically this invention relates to tem perature control devices of the type having a thermal element-arranged to move in accordance with temperature changes and resilient means engaging the thermal element soas to efiect its movement with a snap action, the movement of the thermal element being utilized to actuate switch means comprising fixed and movable contacts. I I

It is an object of this invention to provide in control devices of n this type new and improved means for maintaining the contact pressure between the fixed and movable contacts of the control device until the thermal means are moved with a snap action.

It is another object of my invention to provide in control devices of the aforementioned type new and improved means for maintaining a substantially constant closing force'for' closing the electrical contactswhereby good'electrical contact is made.

It is a further object of my invention to provid'e improved'means for actuating a plurality of contacts with a snap action in'accordanc e with movement of the thermal element.

It is a more specific object of my invention to provide 'a control'idevice having a member which is pivotally mounted independently of the thermal element for operating the circuit controlling means and to provide new and improved means for transmitting the movement of the thermal element to the control member.

A further object of my invention is to provide 'a temperature control device having a new and improved arrangement of elements characterized by its improved switch action, its increased sensitivity, its ruggedness, and its relatively low manufacturing cost. v Further objects and advantages of my invention will become apparent as the following description proceeds, andthe features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a more complete understanding of my invention, reference should be had to the accompanying drawing in which Fig. l is a plan view partially broken away of my improved temperature control. device; Fig. 2 represents avertical the elements of my device in one operative position; Fig. 3 is a vertical section similar to Fig. 2 showing the elements in a difierent operative position; Fig. 4 is a plan view of the control member showing details of its construction; Fig. 5 is a plan view of the temperature responsive member used in my improved control device; and Fig. 6 is a plan view showing details of the transmission member between th control member and the bimetallic member.

Referring to the drawing, this invention has been shown in one form as applied to a tem perature responsive device intended to be used to control rather large currents such as those encountered in a domestic hot water heating sys-. term, but it is to be understood that it is appli-. cable to thermostats to be used in systems where the currents are relatively small and also in systems wherein the currents handled are considerably larger than those ncountered in domestic hot water systems.

As shown in Figs. 1, 2 and 3, the temperature control device comprises a base or supporting member H] formed from a suitable metallic masection taken ontheline .2-2. in Fig. .1 showing terial such as steel. Mounted on one end of the base member I0 is an insulating block H which is adapted to form an end wall of the control device and is provided with recesses and supportingflanges so as to form aterminal block as will more fully appear hereinafter. The block II is made of some suitable insulating material, such as a suitable phenolic condensation product, and is firmly attached to the base member lllby means of a plurality of screws l2 and I3,

Arranged between the base member l0 and the insulating block H and extending longitudinally of the base member is a suitable temperature responsive member l5 which is firmly held in position by means of a pair of rivets I6 located on oppositesides of the screw l3, only one of the rivets being shown in the drawing. The temperature responsive member comprises a relatively thin, resilient, bimetallic blade or strip made of two strips of metal having dissimilar temperature coefiicients of expansion, such as brass and invar, the strips being securely brazed or welded together lengthwise. It will be observed that the end of the member I5 remote from the fixed end is free to move vertically (Fig. 2) in response to changes in temperature.

Provided in the terminal block H is a vertically extending recess Ila which is adapted to receive an adjusting screw l6 which has a rounded end portion I! which is adapted to bear against the member l5 near its fixed end. The adjusting screw I8 is threadedly mounted in a transversely extending U-shaped bracket |8 secured to the base member by means of rivets (not shown), the threaded support being obtained by means of an internally threaded bushing l9 which is mounted in a suitable opening centrally located in the bracket l8. Located between the terminal block H and the bracket I8 is a sheet 29 of suitable electrically insulating material such as mica or a suitable phenol condensation product.

It will be understood that the bimetallic member by reason of its elasticity is forced upward into engagement with the end H of the adjusting screw and, as will more fully appear hereinafter, the temperature at which the control device is operated may be altered by varying the position of the end of the adjusting screw with respect to the base member ID.

Provided on the movable end of the bimetallic bar I is a knife-edge bearing 2| and between this bearing and a bearing 22 secured in a vertically extending integrally formed flange 23 on the base member |8 is interposed a coil spring 24. As illustrated, the spring 24 extends between two cups 25 and 28. The cup 25 is provided with a centrally located depression 21 which receives the knife-edge bearing 2| on the member l5 and the cup 25 is provided with a similar depression 28 which receives the bearing 22. The bearing 22 rather than being formed as a knife-edge has a pivotal or substantially conical form as clearly shown in Figs. 2 and 3 and the seat formed in the cup member 26 is shaped to conform to this bearing. The spring 24 preferably will be formed of a suitable moisture resistant material such as stainless steel.

The bearing pivot 22, as shown, is mounted upon the end of a screw 29 which is threaded into the flange 23 formed in the base member ID. The screw 29 is provided with a slotted end 30 whereby the position of the screw and hence that of the pivot bearing 22 can be changed with an ordinary screw driver or similar instrument. The screw 29 is secured in its adjusted position by means of a lock-nut 3|. that in view of this construction the position of the bearing 22 can be readily adjusted relative to the bearing 2| on the bimetallic member so as to change the tension in the spring member 24.

The screw 29 and its lock-nut 3| are formed of steel rendered corrosive-resistant by cadmium plating.

The function of the pivotally mounted resilient member 24 described above is to move the bimetallic strip l5 quickly between its controlling movement of the bimetallic member is a pivotally mounted control arm, indicated generally by the numeral 34, which is spaced above the bimetallic strip l5 and extends in substantially the same direction as the strip. The control arm is pivotally mounted on a substantially U-shaped bracket 33 which overlies the bimetal member, as shown in Fig. 2, and extends transversely of the base member as shown in Fig. l, the bracket being secured to the base member ID by means of rivets 32. The control arm 34 includes a metal- It will be observed lic frame 3! having a channel-shaped cross-section throughout the greater portion of its length. A shaft 35 is arranged to extend through the frame 31 and the leg portions of the bracket 33 to efiect the pivotal mounting of the arm and the ends of the shaft 35 are flattened to maintain them in their assembled relation with respect to the bracket 33.

Also included in the control arm structure is a block of insulating material 38 which is firmly attached to one end of the frame 31 by means of suitable rivets 39. As will more fully appear hereinafter, the block of insulating material 38 is adapted to support a movable contact member which is arranged to engage fixed contacts so as to control an electric circuit.

In order to control the contact pressure between the movable contact carried on the control arm and the fixed contacts associated therewith and in order to abruptly actuate the movable contact member with a snap action, resilient means are provided which are separate and distinct from the resilient means provided for effecting movement of the bimetallic strip with a snap action. In mounting these resilient means, there is provided on the end of the member 31 remote from the end to which the block 38 is attached a knife-edge bearing 40 having a construction similar to the knife-edge bearing 2| provided on the bimetallic strip l5. Between this bearing 40 and a bearing 4| secured to the flange 23 is interposed a second resilient member 43. As shown, this resilient member 43 is a coil spring somewhat smaller in size than the coil spring 24 and extends between a pair of cup members 44 and 45 having recesses 46 and 41 adapted to receive, respectively, the bearings 40 and 4|. The bearing 4| is substantially conical in form and is mounted on the end of a screw 48 similar to screw 29. The screw 48 is provided with a slotted end 49 whereby the position of the screw and hence that of the pivot bearing 4| may be adjusted longitudinally with respect to the base member ID.

The pivotally mounted control arm 34 and the pivotally mounted resilient means associated therewith substantially resemble a toggle mechanism and since a toggle mechanism depends upon the definite center line for snap action it is necessary to provide a vertical adjustment for the pivot bearing 4| so that the mechanism connected thereto can be arranged for equal displacements on each side of the center line. This vertical adjustment is achieved by means of a slot 5| which is provided in the upper end of the flange 23 and adapted to receive the screw 48. Referring to Fig. 1, it will be observed that the upper end of the flange 23 has a substantially U-shape over a distance slightly greater than the length of the slot 5|. Threadedly supported on the screw 48 is a screw plate 52 which is adapted to be inserted into the channel formed by the upper U-shaped end of the bracket 23. By means of this construction, the screw 48 and hence the pivot bearing 4| may be adjusted vertically with respect to the base member lll. Suitable means comprising the lock-nut 5!) bearing on the washer 53 is provided for holding the screw 48 and the bearing 4| in their vertically and longitudinally adjusted positions.

Arranged to transmit the motion of the bimetallic strip |5 to the control arm 34 is a link 54. As shown in Fig. 6, this link is provided with a pair of slots 55 adjacent one end and a pair of slots 55adjacent its other end. Provided in the member 31 is a transversely extending keyshaped opening 51 having a portion 51a sufliciently wide to permit the unobstructed movement thereinto of an end of thelink 54 and a second portion 51b sufficiently wide to permitthe unobstructed longitudinal movement thereinto of the portion of the link lying between the individual slots of the pair of slots 55. Provided in the member I5 adjacent the movable end thereof is a longitudinally extending key-shaped opening 58 located so as to lie below the opening 5! provided in the member 31. The opening 58 is sufiiciently long to permit the lower end of the link 54 to be inserted thereinto and is provided with a circular portion 58a having a diameter greater thanthe width of the portion of the member 54 lying between theindividual slots of the'pair of slots 56. In assembling the link in its operative position, the lower end thereof is inserted into the elongated opening 56 sufl'lciently far to permit the pair of slots 56 to lie opposite the surface of the member I5. The link is then moved longitudinally into the circular portion 58a of opening and is rotated through an angle of substantially 90 whereby it is locked in position insofar as its connection with the member I5 is concerned. The opposite end of the link is then inserted into the opening 51a until the slots 56 lie opposite the surface of the member 31, The link is then moved longitudinally so that the portion thereof lying between theindividual slots of the pair of slots 56 is moved into the portion 51b of the opening. A washer 59 is then placed adjacent the link 54 and is firmly attached to the member 31 by means of a screw 60 which is adapted to be threaded into an opening 66a provided in the member 31 adjacent the opening 51. It is to be observed that the pairs of slots 55 and 56 of the link 54 are somewhat wider than the thickness of either the member I5 or the member 31 so that a certain amount of play exists in the connection between the member I5 and the link 54 and the control arm 34 and the link. Thi play permits the member I 5 to be moved a small distance vertically without contact assembly comprising a bridging contact L plate 64 which is rotatably mounted upon a pin 65 which is molded into the insulating block 38. The rotation of the movable contact plate 64 is limited by a projection 66 which extends into a slotted section 61 provided in the insulating block 39. As will be observed from thedrawing, the axis of rotation of the bridging contact plate lies substantially perpendicular to the pivot axis of the control arm 34. This permits freedom of action of the bridging contact plate in two planes at right angles to each other, thus assuring proper alignment of the bridging contact plate 64 with the sets of fixed contacts 6| and 62 so as to properly perform a switching function. The

bridging and fixed contacts preferably will be P formed of brass.

The fixed contacts 6I are rigidly secured to terminals 68 which in turn are firmly secured to the block II by means of rivets 69. Suitable binding screws 10 with which electrical connec.

tions are madeare secured to the terminals 68. In a similar manner, the fixed'contacts 62 are secured to the terminals H which are secured to the insulating block by means of rivets I2, suitable binding screws I3 being secured to the terminals II. The terminals and binding screws preferably will be formed of brass and electrical connections are made therewith by directing suitable leads or conductors under the binding screws I0 and 13.

A suitable cover member I4 is providedfor enclosing the operative elements of my improved control device. This covermember is-adapted to rest inside of the flange I5 provided on the base member. I0 and is secured in position by means of drive screws I6 which are received in apertures provided in'the block II.

The cover member I4 is provided with an aper ture 11 through which is adapted to extend the vertically extending abutment I8 integrally formed on the insulating block II which; as shown in Figs. 2 and 3, projects through the aperture for a relativelyshort distance. In addi tion, the upper end of the adjusting screw I6 projects through the opening II, the projecting portion of the adjusting screw being provided with a slot I9 for receiving an ordinary screw driver or similar instrument whereby the adjustment ofthe screw I6 can be efiected conveniently;

Securedto the upper end of the adjusting screw is an index or pointer 80 which cooperates with a suitable temperature scale (not shown) arranged 'on'the' upper surface of the cover I4 so as to assist in making the temperature settings. The abutment I8 is arcuate in form and is provided with relatively flat side portions 8| which act as stops for the index pointer 60 at the lower and upper limits of its temperature setting so that it is impossible to move the ad'- justing screw'beyond'its normal range of operation, that is, beyond the upper and lower limits of the temperature range of operation of the.

device. This is important because it prevents the attendant from moving the adjustment beyond this normal range thereby preventing adjustments'of the device which would destroy its calibration.

As illustrated in Figs. 2 and 3, the cover 14 is I lined with an electrically insulating sheet 82 which may be made from a suitable phenol condensation product. It will also be observed that there is provided on the top of the cover member I4 a removable member 83 which is secured to the cover by means of the tongue and slot construction 84 and screws 85. This removable member 83 is adapted to serve as the nameplate upon which the temperature indicia as well as other nameplate material may be printed.

The base member It is provided with a plurality of apertures 86 through which suitable screw fastening means (not shown) may be passed to secure the base in good thermal relation with the body whose temperature is to be controlled. Thus, for example, the base may be secured to the side walls of a water heater storage tank whereby the'thermally responsive member I5 is caused to respond to the temperature of the water.

In describing the operation of my improved control device, it will be assumed that the temperature adjusting screw I6 has been adjusted to maintain a predetermined temperature and thatthe elements of my device are in theposition shown in Fig. 2. It will be observed that the movable contact 64 engages the fixed contact 6| so as to bridge these contacts and close the circuit controlled by them. It will also be observed that the resilient member 43 is in a position to exert a downward thrust on the end of the frame 31 thereby maintaining a positive contact pressure between the fixed and movable contacts. So long as the temperature of the device which is being controlled is below the predetermined temperature for which the control device is set to operate, the movable contact member will be maintained in engagement with the fixed contact Bl.

As the temperature of the device which is being controlled, a water heater, for example, increases, heat is transmitted to the bimetallic element l and causes this element to move upwardly against the force of the resilient member 24. The initial movement of the bimetallic element is very slow and is called creep. This creep of the bimetallic element, if transmitted to the control arm, would tend to decrease the contact pressure between the movable and fixed contacts. In accordance with my improved arrangement, the bimetallic element is permitted to creep but the means for transmitting the movement of the bimetallic element to the control arm which actuates the contacts is constructed so that the creep movement of the bimetallic element is not transmitted to the control arm. In other words, by means of the play purposely provided in the connection between the link 54 and bimetallic member l5 and control arm 31, the free end of the bimetallic member may move or creep without causing any change in the control pressure between the movable contact and either of the pairs of fixed contacts 5| or 62 until snap occurs. Further more, it is to be observed, therefore, that by means of the play purposely provided in the transmitting means any tendency of the contacts to be altered by the creeping movement of the bimetallic element I5 is eliminated without in any way altering the adjustment of the spring 24 and hence without affecting the amplitude of the temperature responsive device. As a matter of fact, with my improved transmission system and the independent control arm structure, it is possible to decrease the force exerted by the spring 24 on the free end of the bimetallic blade without affecting the contact pressure thereby decreasing the operating temperature amplitude of the device, that is, decreasing the range between the maximum and minimum temperatures at which snap action occurs for any given temperature setting and hence increasing the switc sensitivity.

The play purposely provided in the transmitting means between the bimetallic member l5 and the toggle system is not only sufiicient to substantially prevent variation in contact pressure until snap occurs but it also permits the bimetallic member to accelerate before any motion is transmitted to the control arm toggle system. Thus, when the temperature of the body being controlled attains the predetermined maximum temperature for which the control device is set, the bimetallic element 25 will have moved upwards until the restraining force of the resilient member 24 is relieved. The element l5 then accelerates in an upward direction and with the restraining force of the resilient member continually decreasing the acceleration is rapid and snap occurs. During this rapid acceleration, the play in the connection between azvaies the link 54 and the members l5 and 31 to which the link is connected is taken up and the movement of the bimetallic blade is transmitted to and imparts a kick or thrust on the arm 31 and the control arm toggle system 34 is abruptly displaced from one stationary position, through its definite neutral position, and to its other stationary position thereby causing the movable bridging contact to be moved into engagement with the pair of fixed contacts 62.

It is to be observed that the member 31 is rotated about the shaft 35 provided in the bracket 33 when actuated by the force transmitted thereto by movement of the bimetallic member l5. By means of the resilient member 43, the rotation of the member 37 about this axis is ac celerated once movement is started in a given direction thereby causing the movable contacts associated with the member to be moved quickly and with a snap action. In operation, therefore, the switch arm and its associated resilient member 43 move in a manner similar to an independent toggle mechanism which is actuated between two pcsitions by means of a force exerted thereon, in this instance a force created by the snap movement of a temperature responsive element.

When snap occurs the component elements of my control device assume the position shown in Fig. 3. It will be observed that the resilient member 43 has been moved to a position so as to exert a thrust on the member 37 which tends to maintain a positive contact pressure between the movable contact 64 and the fixed contact 62. The spring 43 will hold the contact 552 closed until the temperature of the device which is being controlled is lowered to a predetermined minimum temperature. When the predetermined minimum temperature is obtained, the member |5 will be snapped downward thereby imparting a kick to the control arm toggle system 34 and effecting movement of the movable contact 64 to the position shown in Fig. 2. By means of the play in the connection between the member 31 and the member l5, no variation in contact pressure will occur as the bimetal strip I 5 slowly cools, the operation of the device upon cooling being substantially the same as that upon heating.

It is apparent that the fixed contacts BI and 62 act as stops to limit the movement of the movable contact member. The tension in the spring 43 is so adjusted that the movable contact member will strike the fixed contacts with sufiicient force to break through any dirt or foreign matter collected thereon and thereby establish a good electrical contact. Since the control arm 34 and the resilient member 43 associated therewith for effecting its action function substantially the same as a toggle mechanism, the closing force with which the movable contact member strikes the fixed contact 6| will be the same with which it strikes the contact 62 and this closing force will be maintained substantially constant long as the tension on the spring 43 is unaltered.

As pointed out previously, the temperature setting of the control device is adjusted by changing the position of the rod l6 relative to the element l5. The amplitude of the device on the other hand, that is, the range between the maximum temperature at which the bimetallic ele ment moves to cause the opening of the contact GI and the closing of the contact 62 and the minimum temperature at which the bimetallic member l5 moves to cause the opening 01 the contact 62 and the closing of the contact BI, is afiected by changing the position of the fixed bearing 22 to control the force exerted by the spring 24 on the free end of the bimetallic element I5. It is desirable to maintain the amplitude which is as small as practicable and this amplitude is determined by the spring force required to insure a positive snap movement of the bimetal blade [5.

In order to vary the contact pressure between the movable and fixed contacts, the fixed bearing 4| may be longitudinally adjusted to vary the tension of the resilient member 43. By moving the fixed bearing to the right, as shown in Fig. 2, the tension is increased thereby increasing the lateral thrust which the resilient member exerts on the knife-edge bearing of the arm 31 and thus increasing the contact pressure.

While I have illustrated my improved control device as having two pairs of fixed contacts to provide a double-pole contact structure, it is obvious that it could be readily adapted to a singlepole structure by the substitution of a suitable stop for one of the pairs of fixed contacts.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not Wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a temperature control device, switch means, temperature responsive means, elastic means associated with said temperature responsive means to cause a snap action movement thereof upon the occurrence of a predetermined temperature, and means for actuating said switch means in accordance with movement of said temperature responsive means, said means including motion transmitting means located between said switch means and said temperature responsive means and loosely connected to each so as to provide a small amount of movement of said temperature responsive means relative to said switch means prior to said snap action movement of said temperature responsive means.

2. In a temperature control device, a resilient bimetallic strip clamped at one end and having its opposite end free to move, pivotally mounted elastic means bearing on said free end of said strip to cause said strip to be actuated quickly and with a snap action, switch means having a fixed contact structure and a movable contact structure, resilient means bearing on said movable contact structure for efiecting a positive contact pressure between said fixed and movable contacts, and means for actuating said movable contact structure in accordance with movement of said bimetallic strip, said last mentioned means including a link loosely associated with both said movable contact structure and said strip so that said contact pressure between said movable and fixed contacts is substantially unchanged until said strip is actuated with a snap action by said elastic means.

3. In a control device, a support, a thin resilient bimetallic strip clamped on said support so as to have one end free to move, pivotally mounted resilient means bearing on said free end of said strip to cause said strip to be actuated with a snap action, a pivotally mounted control arm spaced above said bimetallic strip and extending in substantially the same direction as said strip, switch means having fixed contacts and a movable contact adapted to be actuated by said control arm, pivotally mounted resilient means arranged to bear on said control arm to cause it to be moved quickly between two limiting positions so thatsaid contact means areactuated with a snap action, means for varying the condition of said resilient means so as to alter the contact pressure between said movable and fixed contacts, and link means for transmitting the movement of said bimetal strip to said control arm so that the snap action movement of said strip imparts a kick to said control arm to cause said arm to be actuated, said link means being loosely associated with both said arm and said bimetal strip so that the initial slow movement of said bimetallic strip is not transmitted to said control arm.

4. In a control device actuated in accordance with changes in temperature, a bimetallic strip, elastic means associated with said bimetallic strip for causing it to be actuated with a snap action, means for preselecting the temperature at which said bimetallic strip is actuated with said snap action, control means independently mounted with respect to said bimetallic strip and extending in substantially the same direction as said strip, elastic means associated with said control means for causing said control means to be actuated with a snap action, and a link interconnecting said control means and said bimetallic strip whereby the snap action movement of said strip imparts a force to said control member to cause it to be actuated with a snap action, said link having slots therein for loosely connecting it to both said strip and said control means so that small movements of said strip prior to the occurrence of said predetermined temperature are not transmitted to said control member.

5. In a control device, a pivoted control arm having an opening adjacent one of its ends, switch means actuated by said control arm, elastic means associated with said control arm for moving said arm quickly so that said switch means are actuated with a snap action, a thermally responsive member having one end fixed and the other end free to move and having an opening therein adjacent said free end, elastic means associated with said free end to cause said thermally responsive member to be moved with a snap action, and means extending through said openings in said control arm and in said temperature responsive member for transmitting the movement of said member to said arm, said means being constructed and arranged so that said bimetal member moves a small amount independently of said control arm.

6. In a control device, a pivoted control arm having an opening adjacent one of its ends, switch means actuated by said control arm, elastic means associated with said control arm for moving said arm quickly so that said switch means are actuated with a snap action, a thermally responsive member having one end fixed and the other end free to move and having an opening therein adjacent said free end, elastic means associated with said free end to cause said thermally responsive member to be moved with a snap action, and a link for transmitting the movement of said thermally responsive member to said control arm so that said control arm is moved to actuate said switch means in accordance with temperature changes, said link being loosely supported in said openings provided in said control arm and said thermally responsive member so that said thermally responsive member may move a limited amount relative to said control arm.

7. In a control device, a control arm pivoted intermediate its ends and having an opening adjacent one of its ends, switch means actuated by said control arm, pivotally mounted elastic means bearing on said control arm for moving said arm quickly so that said switch means are actuated with a snap action, a bimetallic member spaced from said control arm and having one end fixed and the other end free to move, said bimetallic member having an opening therein located so as to be in substantial alignment with said opening in said control arm, elastic means associated with said free end of id bimetal member to cause said member to be moved with a snap action, a link extending through said openings in said arm and in said bimetal member for transmitting the movement of said bimetal member to said arm so that said switch means are actuated in accordance with temperature changes, said link having a pair of slots adjacent each end thereof which slots are constructed and arranged to permit a limited amount of play in the connections between said link and said bimetal member and said link and said arm so that said bimetal member may move a small amount independently of said control arm.

8. In a control device, a bimetallic temperatur responsive member fixed at one end and having its opposite end free to move, elastic means associated with said free end and arranged to cause said temperature responsive member to move quickly and with a snap action, means for adjusting the temperature at which said temperature responsive member is actuated by said elastic means, a bracket overlying said temperature responsive member, a control arm pivoted intermediate its ends on said bracket, a contact member attached to one end of said control arm, elastic means bearing on the opposite end of said control arm for causing it to be moved with a snap action, contacts arranged to be engaged by said contact member so as to perform switching functions, a link lying between said thermally responsive member and said control arm and connected thereto to cause said switching functions to be performed in accordance with movement of said thermally responsive member, said link having slots therein adjacent its connection to said thermally responsive member to permit limited movement of said temperature responsive member in accordance with temperature changes independently of said control member.

9. In a temperature control device, a support, a bimetallic temperature responsive element mounted on said support and having one end free to move, elastic means associated with said free end of said bimetallic member to move said member quickly and with a snap action upon the occurrence of a predetermined temperature, means for adjusting said predetermined temperature at which snap action occurs, a bracket mounted on said support and adapted to extend above said bimetallic member, fixed contacts mounted on said support, a control arm pivotally mounted on said bracket, elastic means associated with one end of said control arm to move said arm quickly and with a snap action, movable contact means associated with the other end of said control arm and adapted to cooperate with said fixed contacts to perform a switching function, and a link interconnecting said bimetallic member and said control arm whereby the movement of said bimetallic member with a snap action imparts a thrust to said control arm to cause movement thereof, said link having a pair of recesses adjacent each end thereof which are adapted to cooperate with said bimetallic member and said control arm, respectively, to form a loose connection therebetween whereby movement of said bimetallic member prior to said snap action movement is not transmitted to said control arm.

10. In a control device, a pivotally mounted control arm, fixed contacts, a movable Contact adapted to be actuated by said control arm, pivotally mounted elastic means bearing on one end of said control arm, means for adjusting said elastic means so as to control the contact pressure between said movable and fixed contacts, means for controlling the position of said elastic means so that said control arm will be moved with a snap action equal distances above and below a line passing through the pivots of said elastic means on said control arm, a temperature responsive element spaced from said control arm, and means loosely connected to both said temperature esponsive element and said control arm for transmitting the motion of said element to said control arm so that after a predetermined movernen of said temperature responsive element a thrust is imparted to said control arm to initiate pivotal movement of said arm whereby said arm is moved under the influence of said elastic means from one side of said line to the other so that said movable contact moved into and out of engagement with said fixed contacts in accordance with the occurrence of predetermined temperatures.

11. In a control device having a support, fixed contacts mounted on said support, a movable contact adapted to cooperate with said fixed contacts to perform switching functions, a toggle system associated with said movable contact and adapted to cause said switching function to be performed with a snap action. said toggle system comprising a frame pivotally mounted ori said support, means connecting one end of said frame to said movable contact assembly, a knife edge provided on the opposite end of said frame, a spring adapted to bear on said knife edge to move said frame quickly and with a snap action above and below a neutral line whereby said movable contact is moved with a snap action, a bearing for the opposite end of said spring, means for varying the position of said bearing longitudinally to vary the lateral thrust exerted by said spring on said knife edge, means for vertically adjusting said bearing to cause said frame to be moved equal distances above and below said neutral line, a thin resilient bimetallic member clamped on said support and having one end free to move, elastic means for moving said free end of said bimetallic member quickly and with a snap action upon the occurrence of a predetermined temperature, means for adjusting and preselecting said predetermined temperature, means for transmitting the movement of said bimetallic member to said toggle system whereby said system and its associated movable contact are actuated in accordance with temperature changes, said last mentioned means including means imparting a kick to said toggle system when said bimetallic member is moved with a snap action, and means for providing a limited amount of free movement of said bimetallic element relative to said toggle system whereby the initial slow movement of said bimetallic element is not transmitted to said toggle system.

12. In a control device a base member, a temperature responsive element mounted on said base member so as to have one end fixed and its opposite end free to move, a control arm, means for pivotally supporting said control arm on said base member, means for actuating said control arm in accordance with the movement of said free end of said temperature responsive member, elastic means for causing said control arm to move with a snap action after a predetermined movement of said temperature responsive element, a pair of fixed contacts, movable bridging contact means adapted to cooperate with said fixed contacts to perform a circuit controlling function, and means for rotatably mounting said bridging contact means on said control arm, said last mentioned means permitting limited pivotal movement of said bridging contact means about an axis substantially perpendicular to the axis about which said contact arm pivots so that upon actuation of said control arm said bridging contact means is free to move in two planes lying at right angles to each other to align itself with said fixed contact means to insure proper cooperation therebetween for performing said circuit controlling function.

13. In a control device a base member having a transverse axis and a longitudinal axis, a temperature responsive element mounted on said base member so as to have one end fixed and its opposite end free to move, a pivot pin mounted on said base member so that its axis is substantially parallel to said transverse axis of said base member, a control arm, means for pivotally supporting said control arm on said pivot pin, means for actuating said control arm in accordance with the movement of said free end of said temperature responsive member, elastic means for causing said control arm to move with a snap action after a predetermined movement of said temperature responsive element, a pair of fixed contacts, a movable bridgin contact adapted to cooperate with said fixed contacts to perform a circuit controlling function, and means for pivotally mounting said bridging contact near one end of said control arm so that it is free to pivot about an axis parallel to the longitudinal axis of said base member, said pivotal movement of said control arm and said pivotal movement of said bridging contact producing freedom of movement of said bridging contact in two planes lying at right angles to each other so that said bridging contact plate aligns itself with said fixed contact means to insure proper cooperation therebetween for performing said circuit controlling function.

14. In a control device a base member having a transverse axis and a longitudinal axis, a temperature responsive element mounted on said base member so as to have one end fixed and its opposite end free to move, a pivot pin mounted on said base member so that its axis is substantially parallel to said transverse axis of said base member, a control arm, means for pivotally supporting said control arm on said pivot pin, means for actuating said control arm in accordance with the movement of said free end of said temperature responsive member, elastic means for causing said control arm to move with a snap action after a predetermined movement of said temperature responsive element, a double pole fixed contact structure, a movable bridging contact member adapted to cooperate with said fixed contact structure to perform a circuit controlling function, a second pivot pin mounted on one end of said control arm so that its axis lies substantially parallel to the longitudinal axis of said base member, means for rotatably mounting said bridging contact member on said second pivot pin, and means for limiting the rotation of said bridging contact member about said second pivot pin so as to provide limited pivotal movement thereof about said pin, said pivotal movement of said contact arm about said pin having an axis substantially parallel to the transverse axis of said base member and said pivotal movement of said bridging contact member about said pin having an axis substantially parallel to the longitudinal axis of said base member providing two degrees of freedom of movement of said bridging contact member in two planes lying at right angles to each other to insure proper alignment between said bridging contact member and said double pole fixed contact structure for performing said circuit controlling function.

WALLACE J. EI'IINGER. 

